Extreme heat is fuelling hate speech in America, according to analysis of four billion tweets

Online hate speech can be an indicator of real-world violence, researchers said

Hate speech — whether directed at race, gender, sexual orientation, religion or otherwise — is pretty common on the internet.

But now a new study has found that extreme weather can make the internet an even more unpleasant place.

By analysing about four billion tweets from the United States, researchers found that both extremely cold weather and extremely hot weather led to more hate speech, with a higher rate for extreme heat.

These results point to yet another way the climate crisis could have profound repercussions for human wellbeing – far beyond the direct impacts of weather such as heatwaves, storms and droughts.

“For centuries, researchers have grappled with the question of how climate conditions affect human behaviour and societal stability,” Leonie Wenz, a researcher at the Potsdam Institute for Climate Impact Research in Denmark and one of the study authors, said in a statement.

“Now, with ongoing climate change, it is more important than ever.”

The research team used machine learning to identify about 75 million tweets with hate speech out of four billion posted between 2014 and 2020. “Hate speech” in this context included anything that matched a UN definition — meaning discriminatory language on “religion, ethnicity, nationality, race, colour, descent, gender or other identity factor”.

The team then tagged the tweets by time and location and then matched each with the weather in that location at the time of posting. Results were published on Wednesday in the journal The Lancet Planetary Health.

The fewest number of hate tweets occurred on the most moderate weather days, with temperatures between about 12C (54F) and 21C. But the colder and hotter the days got, the more hate speech the researchers encountered.

Between about -6C and -3C, the number of hate speech tweets rose by 12.5 per cent compared with the most moderate weather days.

On hot days, it was even worse. The researchers found a 22 per cent increase in hate tweets on days where the temperature hit between about 42C and 45C, compared to the most moderate days.

The Independent has contacted Twitter for comment.

The increase in hate speech at temperature extremes held true for a wide variety of political landscapes and income levels.

Low-income, middle class and wealthy areas all saw a rise in hate speech on very hot or cold days, as did cities that voted Democratic in 2016 and cities that voted Republican in 2016.

The same goes for religion. The researchers only had enough data to meaningfully compare Catholic and Evangelical areas, but both predominantly Catholic and predominantly Evangelical communities saw a rise in hate speech during temperature extremes.

“Even in high-income areas where people can afford air conditioning and other heat mitigation options, we observe an increase in hate speech on extremely hot days,” study author Anders Levermann, a researcher at the Potsdam Institute for Climate Impact Research, said via the statement.

The researchers pointed out that other studies have also found a connection between heat and violence or aggression.

The increase in violent, aggressive and discriminatory speech online can have real-world consequences. Online hate speech can be correlated with hate crimes, the authors said in a press release, and targets of online hate speech can face serious mental health challenges.

As the climate crisis causes an increase in extreme weather, particularly extreme heat, these hate speech problems could become more apparent.

Some climate experts have also worried that far-right movements could use concerns of environmental destruction as a way to spread xenophobia and racism.